Smart Agricultural Technology (Mar 2025)
Root cause analysis of noise transfer in an entire tractor system using multi-layer operational transfer path analysis
Abstract
Tractor noise and vibrations adversely affect the health of operators, reduce work efficiency, and interfere with the creation of a comfortable working environment. Electric-powered next-generation tractor systems lack masking effects in engines. Moreover, as various excitation sources contribute to noise, rapid causal analysis of numerous transfer paths is necessary. An operational transfer path analysis (OTPA) is an experimental method used to analyze the energy transfer of noise and vibration. This paper proposed an operational transfer path analysis (OTPA) network for agricultural tractor using a multi-layer transfer function matrix and a contribution calculation method. A root cause analysis of the noise transfer considering the entire tractor system was performed using only the response signals. Acoustic and vibration signals were acquired from 83 sensor channels on the sources and transfer paths of the tractor. Based on the measured signals, an analysis network was constructed using air- and structure-borne paths. The signals predicted by the developed OTPA model matched the overall response level and frequency domain characteristics of the sound pressure signals measured from an actual tractor. Additionally, air- and structure-borne noise contributions were quantitatively evaluated according to the frequency. Analysis results showed that the structure-borne noise was dominant. In addition, the floor panel of cab had a high contribution to the engine 4th-order noise(four times of the engine rotational frequency), and the front glass comprises a structural mode in the 684 Hz band. The contribution from the rear mounts showed that it was the dominant paths for transmitting vibrations to the tractor cab. Moreover, it was higher than that from the front part. This difference indicated that a separate design for the front and rear mounts should be needed. The contribution of air-borne noise increased as the engine speed increased. The air-borne noise was primarily contributed by the wheel noise, with the rear wheels contributing more than the front wheels. The results of this study can contribute to improvements in noise and vibration comfort performance of the agricultural tractor cab.
